An Organic Light-Emitting Diodes (OLED) is considered as one of the most promising display technologies in the future for its advantages in simple manufacturing process, low cost, the ability adjustable color of its emitting light in the region of visible light, suitable for manufacturing a large size display device and the flexible and the like. Especially the white OLED (WOLED) has a power efficiency over 60 lm/W and a lifetime of more than 20,000 hours, greatly promoting development of the WOLED.
As illustrated in FIG. 1 (a), a WOLED employs an organic light-emitting layer 102, the material of which is made up by mixing materials capable of emitting three primary colors of red, green and blue, so that the organic light-emitting layer 102 emits white light. The organic light-emitting layer 102 is disposed between a cathode 101 and an anode 103 so that the white light emitted by the organic light-emitting layer is reflected by the cathode 101 and then exit from a side of the anode 103. In order to improve transmittance and enhance brightness of the WOLED display device, a transflective layer 103′ is displaced at one side of the anode corresponding to a region of a color filter of each color to form a microcavity structure between the transflective layer 103′ and the cathode. As shown in FIG. 1(b), the microcavity structure refers to a structure formed between a reflective layer and a transflective layer with a thickness of micron scale and the principle of the microcavity structure to increase light intensity is that light rays can be continuously reflected between the reflective layer and the transflective layer, and due to resonance effect, in light finally exiting the transflective layer, light with a specific wavelength will be intensified, and the wavelength of light intensified is related to the thickness of the microcavity structure. In a WOLED display device, different pixel units are used for emitting light of different color, and thus microcavity structures in different pixel units should be able to intensify light of different wavelengths (color of which being the same as the one of the color filter corresponding to the microcavity), that is to say, microcavity structures of different pixel units have different thicknesses.
FIGS. 2 and 3 show diagrams of layer structures of two conventional WOLED array substrates. The color filter is located outside the microcavity structure. Based on the principle mentioned above, microcavity structures corresponding to color filters of each color have different thicknesses, such as the structure 300 in FIG. 2 and the structure 400 in FIG. 3. As lights of different colors have different wavelengths, the corresponding microcavity structures are not the same and have different thicknesses. For example, as shown in FIG. 3, Cathode is the cathode of the OLED, Anode is the anode of the OLED and an organic light emitting layer is disposed therebetween (the material thereof generally formed by mixing organic materials capable of emitting three primary colors RGB). R, G, B and W represent light exiting regions of red light, green light, blue light and white light respectively. Red CF, Green CF and Blue CF are color filters of red light, green light and blue light respectively. Microcavity structure of each color light comprises IZO layer or ITO layer disposed above OC layer (protective layer), further comprises a SiNx and SiOx (silicon nitride and silicon oxide) layer for R region, G region and B region, and further comprises an IZO/ITO layer in addition to the anode for R region and B region, with transmittance of corresponding color light increased after white light emitted by WOLED passes through the layers mentioned above. As shown in FIG. 4, the spot lines correspond to transmittance (i.e. brightness) without microcavity structure, and solid lines correspond to transmittance with microcavity structure. Transmittance of blue light is about 1.6 times of original value, transmittance of green light is about 2.5 times of original value and transmittance of red light is about 2.2 times of original value.
As can be seen from FIGS. 2 and 3, the existing microcavity structure increases light transmittance, however, layer structure of the existing microcavity structure is complicated and it is required to manufacture microcavity structures with different thicknesses for regions corresponding to color filters of each color so that the manufacturing process is complicated.